In EUV lithography devices, reflective optical elements for the extreme ultraviolet (EUV) and soft X-ray (SX) wavelength range (e.g. wavelengths of between approximately 5 nm and 20 nm) such as, for instance, photomasks or multilayer mirrors are used for the lithography of semiconductor components. Since EUV lithography devices generally have a plurality of reflective optical elements, the latter have to have a highest possible reflectivity in order to ensure a sufficiently high total reflectivity. The reflectivity and the lifetime of the reflective optical elements can be reduced by contamination of the optically utilized reflective area of the reflective optical elements, which arises on account of the short-wave irradiation together with residual gases in the operating atmosphere. Since a plurality of reflective optical elements are usually arranged one behind another in an EUV lithography device, even relatively small amounts of contamination on each individual reflective optical element effect the total reflectivity to a relatively great extent.
In order to ensure a sufficient lifetime in conjunction with good reflectivity, it is helpful to be able to monitor the composition of the residual gas atmosphere in order, in the event of a rise in the concentration of the gases that lead to contamination, to interrupt the operation of the EUV lithography device and if necessary to carry out cleaning in particular of the optical components. One possibility for in-situ cleaning consists in bombarding them with a jet of atomic hydrogen generated at a glow wire from molecular hydrogen flowing over the latter. On the one hand, relatively long-chain molecules on the surfaces to be cleaned are dissociated by the energy input; on the other hand, the atomic hydrogen reacts with the molecules to form volatile compounds that can be pumped away.
In vacuum systems for EUV lithography which have at least one vacuum chamber and a pump, the contamination in the gas phase should, moreover, always lie below specific limit values since otherwise, during the exposure process, the contamination from the gas phase interacts with the incident radiation in the EUV to soft X-ray wavelength range and is deposited onto the optically utilized areas of the reflective optical element.